/**
 * Determines whether an element uses the "nothing" content model, meaning it
 * must not contain any content. This includes void elements as well as
 * `<iframe>` and `<template>` elements.
 *
 * @see https://html.spec.whatwg.org/multipage/dom.html#the-nothing-content-model
 * @see https://html.spec.whatwg.org/multipage/indices.html#elements-3
 *
 * @param el - The DOM element to check
 * @returns `true` if the element has the "nothing" content model
 */
export declare function isNothingContentModel(el: Element): boolean;